This European Standard specifies the performance requirements for the primary settlement of wastewater at wastewater treatment plants for over 50 PT. The primary application is for wastewater treatment plants designed for the treatment of domestic and municipal wastewater. Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. This standard gives fundamental information about the systems; this standard has not attempted to specify all available systems. Detailed information additional to that contained in this standard may be obtained by referring to the bibliography.